The present invention relates to transmission oil circuits, and more particularly to an oil filter for the transmission oil.
In order to satisfy operators of automotive vehicles, transmission shift quality and performance for automatic transmissions has improved in recent years. Also, vehicle owners expect the vehicles to last longer, which means that the automatic transmissions"" working life requirements have increased. In order to meet these demands, the use of more sensitive electronic solenoids has been required. But these solenoids are much more sensitive to small contaminants in the transmission oil, which can build up to a greater extent over the longer life of the vehicle. Since on previous automatic transmissions, the very small contaminants were not considered a problem, only a coarse media filter was employed on the suction side of the transmission oil circuit just prior to an oil pump. However, this type of filter is proving inadequate at removing the fine particles that can begin to interfere with the operation of the more sensitive solenoids, and may degrade the long term durability of the transmission due to contaminant related wear and valve silting.
To overcome the filtration concern, it is recognized that the addition of a high-efficiency, pressure-side filter will reduce the fine contaminants and hence improve the performance and durability of the automatic transmission. But high efficiency filters can add undesirable pressure drops, thus requiring some type of bypass flow arrangement. This is needed in order to avoid increasing the pump flow demand, and to assure protection for the oil circuit flow during cold starts of the engine or following filter blind off. Also, for efficient filtration, a consistent, stable oil flow is desired. Furthermore, it is desirable that this filter is easily accessible for servicing, if required.
One way to filter the oil in order to avoid contaminants degrading the performance of the transmission is to add an additional oil filter to the transmission oil circuit. Since transmissions are expensive to redesign and it is preferred that a filter have easy access to replace, if needed, it is best to add the filter in the oil circuit external to the transmission. But adding an external oil filter has additional costs, such as the filter element, a filter housing with corrosion protection that will allow it to last the life of the vehicle without failing, additional hose or tubing to connect it into the transmission oil circuit, connection hardware for the new hoses, and possibly bypass valve hardware if full flow filtration is employed. In addition to the cost and complexity added to the oil circuit, the external filter adds more potential leak paths to the oil circuit, which may increase warranty costs of the vehicle.
Thus, it is desirable to have a transmission oil filter that will efficiently filter fine contaminants from transmission oil, while minimizing the costs and potential leak paths for such a filter.
In its embodiments, the present invention contemplates an oil cooler assembly for use with an automatic transmission system of a vehicle. The oil cooler assembly has a first end pipe and a second end pipe, with the first end pipe including an oil inlet, adapted for receiving oil from the transmission system, and an oil outlet, adapted for returning oil to the transmission system, and a dividing plate sealingly mounted in the first end pipe between the oil inlet and the oil outlet, with the dividing plate including a flow control orifice therethrough. A core is contained between the first end pipe and the second end pipe, including a first set of ribs extending therebetween adapted for allowing oil to flow from the first end pipe to the second end pipe and a second set of ribs extending therebetween adapted for allowing oil to flow from the second end pipe to the first end pipe. The oil cooler assembly also has an oil filter sealingly mounted in the first end pipe about the orifice and adapted to thereby cause oil flowing through the orifice to flow through the filter.
The invention further contemplates a method of filtering oil in an oil cooler circuit adapted for use with a vehicle automatic transmission system, with the method comprising the steps of: receiving oil in a first end pipe of an oil cooler through an inlet; flowing a first portion of the oil through a first set of ribs in an oil cooler core to a second end pipe; flowing the first portion of the oil through a second set of ribs in the oil cooler core back to the first end pipe; flowing the first portion of the oil out of the oil cooler through an outlet; flowing a remaining portion of the oil through an orifice in a dividing plate which separates the inlet from the outlet in the first end pipe; filtering the remaining portion of the oil that passes through the orifice; and flowing the remaining portion of the oil out of the oil cooler through an outlet.
An embodiment of the present invention allows a transmission oil filter to be integrated into an automatic transmission oil cooler, using the oil cooler itself as the housing for the oil filter.
An advantage of an embodiment of the present invention is that no additional housing is needed in order to add a transmission oil filter into a transmission oil circuit.
Another advantage of an embodiment of the present invention is that the cost of adding a transmission oil filter capable of filtering fine contaminants is greatly reduced.
A further advantage of an embodiment of the present invention is that a transmission oil filter capable of filtering fine contaminants is added while still minimizing the number of potential leak paths for the oil in the transmission oil circuit.
An additional advantage of an embodiment of the present invention is that the fine contaminant filter is added without significantly increasing the transmission oil pump flow demand, while also allowing for protection of oil circuit flow during cold engine starts and filter blind off conditions.